1. Field of the Invention
The invention relates to a sensor chip, and more particularly, to a pressure sensor chip for fingerprint recognition.
2. Description of the Prior Art
In recent history, the technology of fabricating sensor chips has developed and expanded to incorporate the recognition and sensing capabilities of a sensor chip into a semiconductor chip to achieve minimal size. The sensor chips, depending on various designs and requirements, can be fingerprint sensors or image sensor chips. The conventional method of fabricating sensor chips involves forming a sensing region on the active surface of the semiconductor chip, in which the sensing region should be covered during the packaging process. After the packaging process is completed, the sensor chip can be accessorized to portable electronic devices, including: mobile phones, notebook computers, and PDA's. The sensor chip is commonly utilized in said portable electronic devices for facilitating user fingerprint recognition and capturing images.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram showing the active surface of a sensor chip 100 according to the prior art. FIG. 2 is a diagram showing a cross-section of the sensor chip 100. As shown in FIG. 1, the sensor chip 100 is fabricated from a semiconductor chip 110, in which the semiconductor chip 110 includes an active surface 111 and a corresponding back surface 112, as shown in FIG. 2. The active surface 111 includes a sensing region 113, a plurality of sensing devices (not shown), and a plurality of bonding pads 120 disposed on the active surface 111, in which the sensing region 113 should not be covered by a molding compound 230 during the packaging process. During the packaging process, the back surface 112 of the sensor chip 100 is first attached to a chip carrier 210 and a plurality of bonding wires 220 are utilized to electrically connect the bonding pads 120 to the chip carrier 210. Next, a molding compound 230 is formed to seal the bonding wires 220 and part of the active surface 111 containing the bonding pads 120 while exposing the sensing region 113, in which the molding compound 230 can be formed via dispensing or molding processes. However, an overly low speed of the dispensing process will result in an uneven shape of the molding compound thereby resulting in the ability to control the area of the active surface to be uncontrollable. Similarly, when the molding process is performed, the mold flash will contaminate the sensing region 113 and influence the function of the sensor chip. Furthermore, when the sensor chip 100 is applied to fingerprint recognition, the active surface 111 must be touched frequently by fingers and this further increases a peeling phenomenon to occur at the edge of the passivation layer 130 on the active surface 111.